The present invention relates generally to radar signal processors and more particularly to radar signal processors which are capable of transmitting both clutter and target signals to a remotely located radar display.
Many modern radar systems have signal processing circuitry which is designed to eliminate radar clutter signals provided to a radar display. In many systems only the target information is transmitted to the display. For example, many radar signal processors incorporate a sweep-to-sweep correlator, azimuth integrator, and thresholding circuitry which helps to eliminate random pulse interference and noise. Many systems, however, utilize thresholding circuitry which only transmits target signal data and which suppresses radar clutter signals. This is accomplished by having an adaptive threshold which eliminates the clutter. In certain situations, it may be advantageous to view the clutter which is observed by the radar system. Allowing the operator the opportunity to view the clutter on the radar display may provide assistance in determining the presence of targets. For instance, if a potential target is moving toward a highly cluttered area, the operator may have the opportunity to change thresholding levels in order to see the target more clearly in the cluttered background or to provide manual assistance in tracking the target. Also, in air traffic control applications, it is desirable to know the location of weather clutter so that air traffic may be rerouted to avoid inclement weather. Heretofore, radar systems which allowed display of clutter and moving targets required a wide bandwidth communications link between the signal processor and radar display. This wideband communications link was required in order to continuously transmit the clutter information during each sweep of the radar antenna scan.
Thus, a problem common to most prior art systems relates to attempts to use a narrow band, low cost communications data link between the signal processor and the radar display. For example, use of a medium quality radar transmission line as a communication link was described in "Economical Radar Information Transmission Utilizing Band Compression Techniques", by T. Furuhashi et al, IEEE International Radar Conference Record, September 1975, pages 164-169. This system utilizes a resolution reduction of the radar video in azimuth by a 4:1 ratio and in range by 2:1 to transmit 0.3 megahertz video with targets and clutter over a 40 kilohertz communications line.
Thus, it would be an improvement in the radar art to provide a system which allows for the display of clutter on the radar display when desired by the operator and which allows the use of a low cost, narrow bandwidth communications data link between the signal processor and the radar display.